Ashwani K. Malhotra

MCM-D/C packaging solution for IBM latest S/390 servers

The G5, fastest member of the S390 server family, was announced in May of 1998. The multichip module (MCM) used consists of 29 CMOS chips on a 127.5 mm glass ceramic substrate with 6 levels of thin films (TF) including 1 signal plane pair. The G5 system performance exceeded 1,000 MIPS. This breakthrough performance resulted from the synergy created by combining IBMs leadership technologies in CMOS high frequency microprocessor design with advanced packaging and flip chip interconnections. From a substrate perspective, IBM moved from alumina ceramic and Mo conductors to glass ceramic and Cu, and from TF redistribution (4 levels) to TF wiring (6 levels). This paper discusses the TF implications from a change of substrate material and increased wiring density, as well as the need to implement a polyimide cushion layer as part of the pin grid array (PGA) fabrication process to support 4224 I/Os.